This invention is related to a breathable multi-ply barrier film and a breathable barrier film laminate comprising said breathable multi-ply barrier film and a nonwoven web. The laminate is particularly useful as an outer cover for disposable diapers and other disposable personal care products, and for breathable surgical gowns, surgical drapes, coveralls, and other breathable protective apparel. In addition, this invention is directed to a method for producing the breathable multi-ply barrier film and laminate.
The present invention is directed to breathable barrier films and laminates of breathable barrier films and nonwoven materials. Such laminates have a wide variety of uses, particularly in the areas of limited use and disposable items.
Films have been traditionally used to provide barrier properties in limited use or disposable items. By limited use or disposable, I mean that the product and/or component is used only a small number of times, or possibly only once, before being discarded. Examples of such products include, but are not limited to, surgical and healthcare related products such as surgical drapes and gowns, disposable work wear such as coveralls and lab coats, and personal care absorbent products such as diapers, training pants, incontinence garments, sanitary napkins, bandages, wipes and the like.
In protective apparel, such as hospital gowns, films are used to prevent cross exchange of microorganisms between the wearer and the patient. Although these films are generally effective barriers with respect to water vapor and the like, they are not aesthetically pleasing because their surfaces are smooth and either feel slick or tacky, and they are visually unappealing, making them less desirable in apparel applications and other uses where they are in contact with human skin. Thus, it is desirable that these items be more cloth-like, both from a tactile and visual standpoint. For example, garment-like isolation gowns for use in hospital environments most likely would increase the comfort of the wearer while reducing the apprehensiveness of the patient.
A primary purpose of the film in such laminates is to provide barrier properties. However, there is also a need that such laminates be breathable so that they can transmit water vapor which, in turn, requires that the film be breathable. Apparel made from laminates of breathable or microporous films are more comfortable to wear because they reduce the water vapor concentration and the consequent skin hydration underneath the apparel item. Breathable films and a method for producing such films are taught, for example, by U.S. Pat. No. 3,844,865; and breathable laminates employing porous films and nonwoven materials are taught by U.S. Pat. No. 5,560,974 and U.S. Pat. No. 5,169,712.
In order to be suitable for use in surgical garment applications, as well as other protective apparel, suitable barrier film laminates must meet the requirements of ASTM Standard F-1670 and ASTM Standard F-1671, which standard test methods provide a basis for assessing the effectiveness of materials used in protective clothing for protecting the wearer against contact with body fluids that potentially contain blood-borne pathogens. Conventional film laminates comprise a single layer of microporous film and, as such, defects and/or microscopic holes in the film layer caused by film imperfections frequently cause failure of the laminate to satisfy the requirements of ASTM barrier performance.
In known processes for forming a nonwoven web/film and/or nonwoven web/film/nonwoven web laminate using heavily loaded film, film containing a filler, such as calcium carbonate (CaCO3) particles, is stretched and thinned so as to render it moisture vapor permeable. However, bonding of the nonwoven web to the film sometimes produces small holes not visible to the naked eye due to imperfections in the film. These small film holes lead to a failure of the material to pass the ASTM tests for barrier performance.
Accordingly, it is one object of this invention to provide a method for producing breathable barrier film laminates which reduces or eliminates failures caused by these film imperfections.
It is a further object of this invention to provide an inexpensive laminate for use in surgical drapes and gowns, and various other protective apparel that has a soft outer cover and breathability properties.
These and other objects of this invention are achieved by a method for producing a moisture vapor permeable multi-ply film in which a polymer suitable for use as a polymeric film and comprising a filler having a particle size suitable for pore formation is extruded to form an extruded film. The extruded film is hot blown, resulting in formation of a hot blown film bubble. The hot blown film bubble is collapsed and trimmed, forming a multilayer film, after which the multilayer film is stretched, forming a plurality of micropores in both layers of the multilayer film. To form the breathable barrier film laminate of this invention, the stretched, microporous, multilayer film is bonded to a nonwoven web layer, forming a nonwoven/film laminate. Because the barrier film of this invention is a multilayer film, the probability of an imperfection in any one area of one layer of the film aligning with an imperfection in the other layer of the film is greatly reduced or eliminated, thereby substantially increasing the probability that the material produced in accordance with the method of this invention will meet ASTM test requirements.
In accordance with one preferred embodiment of this invention, the multilayer film is stretched to a length in the range of about 350 to 500% of its initial length. The resulting film has a water vapor transmission rate (WVTR) in the range of about 1200 grams per square meter per 24 hours (g/m2/24 hours) (measured by ASTM Standard Test E96-80 with CELGARD(copyright) 2500 as control).
Laminates of this invention have a wide variety of uses including, but not limited to, items such as surgical drapes and gowns, as well as various articles of clothing, either the entire article or simply as a component thereof.